In recent electronic amplifiers devised to drive a capacitive load, for example, in audio amplifiers usable in battery-operated portable devices, there may be a need to have reduced current consumption. A known electronic amplifier usable to drive a capacitive load generally comprises a differential amplifier, which includes differential input terminals to receive an input signal Vin, for example, a substantially sinusoidal voltage signal. In addition, the differential amplifier operates to amplify the input signal Vin in order to provide first V1 and second V2 output voltages to respective differential output terminals of the amplifier. The first V1 and second V2 output voltages have opposite polarity in respect to a common mode voltage VCM.
The differential amplifier is powered from a power supply potential VDD and a ground GND potential, the common mode voltage VCM is in the middle between the power supply VDD and ground GND in order to reach maximum swing of a differential output signal Vout=V1−V2. The differential amplifier described comprises an output stage which drives the capacitive load. Particularly, the output stage is so configured that energy from the power supply potential VDD is consumed both during charging periods of the capacitive load and during discharging periods as well. In fact, conduction of output transistors forming the output stages of the differential amplifier is handled during the mentioned charging/discharging periods so that to define with the capacitive load itself a conduction path for the current flowing from the power supply potential VDD and the ground potential GND both in the charging periods and in the discharging periods. Therefore, when the differential amplifiers are used in portable device, a large amount of current consumption may reduce the life of the power supply batteries, thereby compromising the portability of the device itself.